The use of a breathing tube to allow a swimmer to maintain facial position below the surface of the water is well known. Snorkels are useful in clear water to allow observation of underwater plant and animal life.
A swimmer will stroke with ideal efficiency when his or her face is in the water, but the back of the head remains out of the water. Many swimmers find breathing difficult while maintaining ideal stroke form, as pushing the chin forward to lift the back of the head out of the water creates a strain in the trachea.
Moreover, when a swimmer raises his or her head to breathe, the hips and legs sink into the water. A two-inch vertical lift of the head can result in a four- to six-inch drop of the hips, and a corresponding eight- to twelve-inch drop of the feet. This departure from ideal stroke form can double the frontal surface area offered to the water, thereby doubling the water resistance encountered by the swimmer.
Because a snorkel allows the swimmer to breathe without raising his or her head, snorkels have been used to assist athlete's train for competition. Under these circumstances, it is important that the swimmer can easily purge water from the breathing tube during use, to prevent interruption of his/her training.
Traditional purge valve designs used for diving are not suitable for use in swimming. In order to activate a conventional diving purge valve, the reservoir surrounding the valve must be filled with water above the mouth area. When the user sharply exhales, water in the snorkel is forced upward, and provides sufficient back-pressure to offset external water pressure and activate the purge valve. Accumulated air and water are expunged, and the swimmer can breathe again.
When a scuba diver uses a snorkel, water normally fills the entire snorkel and the conventional purge valve works adequately. However, when a snorkel is used primarily for surface activities such as swimming and snorkeling, the snorkel will contain some water but will not ordinarily become filled.
The conventional diving-type purge valve is thus unsuited for swimming and snorkeling, as a relatively large volume of water must accumulate in the snorkel before it can be purged. This accumulated water consumes valuable air space, decreasing the flow of air available to the swimmer. Accumulated water can also splash into the swimmer's airway, making breathing uncomfortable.
There is thus a need in the art for a snorkel design that permits a swimmer to efficiently purge the snorkel of water during use, without having to wait for the snorkel to fill with a relatively large volume of water.